feat: add random message selection and theme toggle

script.js picks a random entry from MESSAGES on load and on each "Check
again" click, and persists the chosen colour scheme in localStorage.
messages.js holds the MESSAGES array as a placeholder template to be
filled in with content.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

messages.js

@@ -0,0 +1,18 @@
+/* Messages for "Why is the DLR shut today?"
+ *
+ * Fill this array with your own reasons. One string per entry.
+ * On every page load (and every "Check again" click) one entry is
+ * picked at random and shown in the centre of the screen.
+ *
+ * Keep them short — roughly a sentence — so they fit the large display
+ * text. HTML is NOT rendered; entries are inserted as plain text.
+ *
+ * Replace the placeholders below with your own content.
+ */
+
+const MESSAGES = [
+  "PLACEHOLDER: write your first reason here",
+  "PLACEHOLDER: write another reason here",
+  // Add as many entries as you like, one per line:
+  // "Your reason here",
+];